A proper combination of movement and stillness: the interaction effect of sleep duration and physical activity on longitudinal cognitive performance in Chinese middle-aged and older adults.

Previous studies have shown that both nighttime sleep duration (NSD) and physical activity (PA) are independently associated with geriatric cognition. However, most of these studies are cross-sectional and do not account for the interaction between NSD and PA, and the relationship between midday nap duration (MND) and cognition is unclear. Data collected between 2011 and 2018 were obtained from the China Health and Retirement Longitudinal Study (CHARLS). Generalized linear models and generalized estimating equations were used to analyze the impacts of NSD, MND, total sleep duration (TSD, NSD + MND), PA, and their interactions on both baseline and longitudinal cognitive performance. Combining the results of baseline and longitudinal univariable analyses, inverted U-shaped patterns were found, with the best choices being the 6-8 h of NSD and TSD (P < 0.05), the 0-90 min of MND (P < 0.05), and moderate PA (MPA, P < 0.05). The interaction analysis revealed that individuals with sleep duration of 6-8 h or < 6 h who engaged in MPA demonstrated significantly better cognitive performance and maintenance (P < 0.05), but for those with > 8 h of sleep, little significant differences in cognitive outcomes were observed across varying PA regimens. Considering both univariable and interaction effects, an optimal combination of movement and stillness for better cognitive function is to maintain 6-8 h of nighttime sleep, take a midday nap, and actively engage in MPA.